Of the various types of leak detectors known in the prior art, some are particularly suited to appliance leaks and to various plumbing leaks. An example is provided by those that can be fitted under a sink and under a plurality of appliances. A problem with such detectors is that they are typically battery operated. Remembering to change a battery is inconvenient. Electrical devices in a wet or humid environment can also be problematic. Complexity further exacerbates problems. What has been needed is a purely mechanical device that is inexpensively manufactured, easily installed, and easy to replace. The present kit provides these advantages.